Long-time signatures of non-Markovianity in open quantum systems

Memory effects in open systems typically manifest on short timescales, as their contribution is overwhelmed by thermal dissipation over long times. Furthermore, standard metrics quantifying such non-Markovian evolution are tomographic in nature, making them impractical for experimental observation [1]. Given their versatility and ease of implementation, spectroscopic measurements present an attractive alternative to characterize such dynamics. In this talk, I will first discuss an approach based on a time-dependent master equation and apply it to the archetypal qubit-resonator system. We obtain an analytical expression for the qubit emission spectrum that captures persistent non-Markovian features in the steady state [2]. I will then introduce a new approach which allows such analysis to be done directly in the frequency domain, bypassing the cumbersome calculation of two-time correlators. Our results highlight the parameter regimes where deviations from Markovianity are most pronounced and how they may be tuned via the choice of interaction and resonator dynamics.